Biodiversity: The Variety of Life
≈ 18 minBiodiversity is the variety of living things found in a place. It is measured at more than one level:
- the number of different species present;
- the variety within a species (think of all the different varieties of maize a farmer can plant);
- the variety of habitats — the different kinds of places available for organisms to live.
A species is a group of organisms that are alike and can breed with one another to produce offspring that can themselves breed. Lions are one species; leopards are another.
South Africa is one of the most biologically diverse countries on Earth. We hold about 10% of the world's known plant species on roughly 2% of the world's land, along with a huge variety of birds, reptiles, insects and mammals.
Worked example — comparing two plots. A learner marks out two squares of 1 m × 1 m.
- Plot A, in a maize field, contains 40 maize plants — 1 species.
- Plot B, in Cape fynbos, contains 7 buchu, 5 erica, 3 restio and 1 protea — 4 species, 16 individual plants.
Plot A has more plants, but Plot B has far higher biodiversity, because biodiversity counts the number of different kinds, not the number of individuals.
Many fynbos species are endemic — they occur naturally in one place on Earth and nowhere else. Roughly two out of every three fynbos plant species are found only in the Cape.
Two square plots are surveyed. Plot A (a maize field) contains 40 maize plants. Plot B (fynbos) contains 16 plants of 4 different kinds. Which plot has the higher biodiversity?
What word describes a species that occurs naturally in one area of the world and nowhere else — such as many Cape fynbos plants?
In a 1 m × 1 m fynbos plot a learner records: 7 buchu plants, 5 erica plants, 3 restios and 1 protea. How many different species did she record?
South Africa holds about 10% of the world's known plant species on roughly 2% of the world's land area. Which conclusion does this best support?